Field of the Invention
The present invention pertains to endoscope couplers for optically and mechanically coupling an endoscope to a video camera. More particularly, the invention relates to endoscope couplers having a focus control lens movable in a permanently sealed chamber.
Description of the Prior Art
Endoscopes have become widely utilized in surgery for viewing body cavities and organs to permit performance of diagnostic and surgical procedures internally without the need for invasive surgical procedures. An endoscope is typically inserted through a small incision portal providing access to the body cavity. A lens at a distal end of the endoscope is positioned to receive light reflected from a site to be observed, and images of the site can be viewed remotely to conduct histological examinations and to perform closed, or endoscopic, surgery. As used herein, the term endoscope refers generically to viewing devices for remotely observing otherwise inaccessible body cavities with minimal trauma and intrusion, including but not limited to arthroscopes, colonoscopes, bronchoscopes, hysteroscopes, cystoscopes, sigmoidoscopes, laparoscopes and ureterscopes.
Endoscopes are sometimes supplied with an eyepiece at a proximal end thereof, and relay lenses in the endoscope typically produce an image for direct viewing through the eyepiece. However, adaptation of video camera technology to endoscopy imaging has enabled the output image of an endoscope to be viewed on a video monitor. Specifically, a video camera is electronically coupled to the video monitor and optically and mechanically coupled with the proximal end of the endoscope. Indirect or video monitor viewing of endoscopic images provides numerous benefits over direct viewing through an eyepiece, including: protection of a direct viewer's vision from high intensity illumination passed through the endoscope and reflecting off bodily tissue; enhancement of operator comfort and freedom of movement; increased endoscope utility and efficiency; reduction in the time required to conduct many endoscopic procedures; simultaneous viewing of endoscopic images by more than one person; and recordation and real time transmission of surgical procedures.
An endoscope coupler is required to couple the proximal end of the endoscope to the video camera, illustrative endoscope couplers being shown in U.S. Pat. Nos.: 4,569,333 (Bel et al); 4,611,888 (Prenovitz et al); 4,722,000 (Chatenever); 4,740,058 (Hori et al); 4,781,448 (Chatenever et al); 4,807,594 (Chatenever); 4,844,071 (Chen et al); 4,851,866 (Ciarlei et al); 4,863,304 (Bauer et al); 4,969,450 (Chinnock et al); and 5,056,902 (Chinnock et al). Endoscope couplers usually include a cylindrical body closed at opposing ends by end windows and containing a lens holder carrying one or more lenses longitudinally movable within the body to adjustably focus an image from the endoscope onto a focal plane of the camera. A focusing ring is mounted on the body and is coupled with the interior lens holder to selectively move the lens holder and the lens in response to movement of the focusing ring. Mechanical interconnection between the focusing ring and the lens holder (e.g., by cam pins on the focusing ring riding in slots in the lens holder) permit longitudinal movement of the lens holder in response to focusing ring rotation while preventing rotation of the lens holder.
In order to maintain sterile surgical conditions, endoscope couplers must be sterilized before and after each use. Prevailing methods for sterilizing surgical instruments include steam autoclaving, immersion in sterilization liquid and gas sterilization. Steam autoclaving is commonly performed under extremely high temperatures, and most endoscope couplers are unsuitable for sterilization by steam autoclaving due to their inability to withstand high temperatures without structural degradation and damage. Therefore, the preferred protocol for sterilizing endoscope couplers involves total immersion in disinfecting liquid or prolonged exposure to sterilizing gas. Because gas sterilization necessitates specialized sterilization apparatus and is usually relatively expensive, the most preferred method of sterilizing endoscope couplers involves total submersion of the endoscope coupler in sterilizing liquids, such as glutaraldehyde based solutions. Sterilization of endoscope couplers by soaking in sterilizing liquids is simple to perform, requires no highly customized equipment or specialized labor and is relatively inexpensive. However, conventional endoscope couplers are adversely affected when sterilized by submersion in disinfecting solutions or by gas sterilization. For example, the mechanical drive mechanism interconnecting the focusing ring and the lens holder in conventional endoscope couplers allows sterilizing liquid or gas to seep into the coupler body around the drive mechanism. Specifically, cam pin and slot drive mechanisms, as well as other mechanical linkages between the focusing ring and the lens holder, provide fluid communication between the interior and exterior of the coupler body. Liquid or gas entering the coupler body can create residue on and spot the end windows as well as the interior lens whereby the image presented to the video camera is significantly impaired. Even small amounts of sterilizing liquid or gas in the coupler body can produce serious consequences if deposited on the end windows and/or the lens. Further, minute residual amounts of liquid in the coupler body can produce condensation on the windows and lens during use as heat from illumination directed through the endoscope causes fogging of the relatively cooler windows and lens. Condensation on the windows and lens detracts from image clarity at the video camera and can seriously hamper diagnostic and surgical procedures. Frequently, condensation does not occur until heat from illumination produces a relatively high temperature gradient between the proximal end of the endoscope and the endoscope coupler and, by that time, the surgical procedure is usually well under way. In many cases, the procedure must be temporarily suspended to permit replacement of the endoscope coupler. Moreover, endoscope couplers known to experience problems due to residual moisture must be reconditioned through dismantling, cleaning, drying and reassembling, a process that is time consuming and absorbs scarce personnel resources. Although most conventional endoscope couplers include seals at cam and slot for preventing leakage of sterilizing fluid into the coupler body, these seals are usually O-ring or quad-ring seals that perform inadequately under fluid and gas sterilization conditions. Such seals generally fail to prevent entry of fluid or gas into the coupler body and have the further disadvantage of increasing the structural and manufacturing complexity and cost of the endoscope coupler.
It is known in the prior art to provide an endoscope coupler with a sealed chamber containing a lens focused by means of a magnetic field. Specifically, U.S. Pat. No. 5,056,092 (Chinnock et al) discloses an annular magnet disposed concentrically about the sealed chamber and arranged to move axially in response to rotation of a focusing ring. The interior focusing lens is supported in a magnetically permeable actuator housing defining a closed flux path with the exterior magnet so that the actuator housing and focusing lens are moved axially in response to axial movement of the magnet. This patent also discloses that the actuator housing may be an annular magnet. The resulting coupler structure permits the chamber containing the lens to be effectively sealed since there are no mechanical elements extending into the chamber. However, manufacture of the control arrangement is relatively expensive because each annular magnet must be custom made. More specifically, a ring magnet, once formed, cannot be machined to tailor its fit and orientation in the final assembly. The fit and orientation of the control magnet are crucial in the Chinnock et al device in order to assure accurate control over the actuation housing position. Accordingly, the magnet must be manufactured to such close tolerances as to preclude the use of mass production techniques.
Another disadvantage of many endoscope couplers is that the structure for connecting the coupler with the proximal end of an endoscope and a video camera is so complex as to make it difficult for the coupler to be attached and detached. Frequently, endoscope couplers are sterilized separately from endoscopes and video cameras, and considerable time and effort is required when complex connecting mechanisms are utilized to disconnect a coupler from an endoscope and a video camera prior to sterilization and to reattach the coupler to an endoscope and a video camera after sterilization and prior to use. Moreover, many connecting devices are limited for use with certain sizes and types of video cameras, and attachments must be utilized to adapt the endoscope couplers accordingly. Such attachments are usually difficult to apply to endoscope couplers and similarly require significant time and labor for assembly and disassembly.
A further drawback of conventional endoscope couplers is that the focusing rings commonly do not provide an acceptable tactile response with the result that the focusing rings feel too loose or too tight. Consequently, it is difficult for an operator to gain tactile control during focusing, and lack of proper "feel" detracts from the functional utility of most endoscope couplers. Until the present invention, there has been no low cost and functionally effective endoscope coupler formed water and gas-tight while allowing the focusing ring to drive the lens assembly in a tactually responsive manner without rotation of the lens assembly within the coupler.